DISEASE CHARACTERISTICS:

* Must have undergone a hysterectomy (total abdominal, vaginal, radical, or laparoscopic-assisted vaginal) within 7 weeks prior to study entry

* Patients with endometrial cancer must have also undergone a bilateral salpingo-oophorectomy
* Histologically confirmed diagnosis of 1 of the following:

* Endometrial cancer meeting 1 of the following criteria:

* Stage IB grade 3, IC grade 1-3, IIA, or IIB disease requiring postoperative pelvic radiotherapy
* Unstaged (no lymph node dissection or sampling) stage IB grade 2 disease
* Stage IIIC with all of the following:

* Pelvic lymph node positive only
* Para-aortic nodes sampled negative
* Not receiving chemotherapy
* Cervical cancer meeting 1 of the following criteria:

* Post-radical hysterectomy and requires postoperative pelvic radiotherapy due to any of the following:

* Positive pelvic nodes (negative para-aortic nodes)
* Microscopic parametrial involvement and negative margins
* Disease qualified by Sedlis criteria must have 2 of the following risk factors:

* 1/3 or more stromal invasion
* Lymph-vascular space invasion
* Large clinical tumor diameter (≥ 4 cm)
* Post-simple hysterectomy with negative margins and negative nodes by CT scan, MRI, or positron emission tomography-CT scan
* No requirement for extended-field radiotherapy beyond the pelvis
* No histologically confirmed papillary serous, clear cell, or neuroendocrine (either large or small cell) disease, endometrial stromal sarcoma, leiomyosarcoma, or malignant müllerian mixed tumor
* No evidence of metastatic disease outside of the pelvis
* No microscopic involvement of the resection margin (< 3 mm)

PATIENT CHARACTERISTICS:

* Zubrod performance status 0-2
* WBC (white blood cell count) ≥ 4,000/mm³ (cervical cancer patients only)
* Absolute neutrophil count ≥ 1,800/mm³ (cervical cancer patients only)
* Platelet count ≥ 100,000/mm³ (cervical cancer patients only)
* Hemoglobin ≥ 8.0 g/dL (transfusion allowed)
* Serum creatinine ≤ 2.0 mg/dL (cervical cancer patients only)
* Creatinine clearance ≥ 50 mL/min (cervical cancer patients only)
* AST (aspartate aminotransferase) ≤ 2 times upper limit of normal
* Bilirubin ≤ 2 times upper limit of normal
* Patients must not exceed the weight and size limits of the treatment table or CT scanner

* No mental status changes or bladder control problems that would preclude study compliance with bladder-filling instructions
* No active inflammatory bowel disease
* No severe, active, concurrent illness, defined as any of the following:

* Unstable angina and/or congestive heart failure requiring hospitalization within the past 6 months
* Transmural myocardial infarction within the past 6 months
* Acute bacterial or fungal infection requiring IV antibiotics
* Chronic obstructive pulmonary disease exacerbation or other respiratory illness requiring hospitalization or precluding study therapy
* Hepatic insufficiency resulting in clinical jaundice and/or coagulation defects
* AIDS
* No history of allergy to cisplatin (cervical cancer patients)
* No prior invasive malignancy (except nonmelanoma skin cancer) unless disease-free for ≥ 3 years

PRIOR CONCURRENT THERAPY:

* See Disease Characteristics
* No prior radiotherapy to the pelvis that would result in overlap of radiotherapy fields
* No prior platinum-based chemotherapy (cervical cancer patients)
* No concurrent prophylactic growth factors (e.g., filgrastim \[G-CSF\], sargramostim \[GM-CSF\], or pegfilgrastim)
* No concurrent prophylactic thrombopoietic agents
* No concurrent amifostine or other protective agents